Fiberizers, also called hammermills or disintegrators, are employed in the production of products requiring an absorbent fibrous airfelt pad. Using fiberizers, sheets of fibrous material are disintegrated into individual fibers which are transmitted to a foraminous conveyor on which an airfelt is formed. Fiberizers employ impact elements such as hammers or teeth carried on the periphery of a cylindrical rotor. To disintegrate the fibrous sheets, they are fed through infeed slots which lead to an anvil and into contact with the impact elements on the periphery of the rotor. The impact elements have faces positioned to hit the sheets, the direct impact causing individual fibers to be separated and the sheets to be fiberized. This separation of fibers by direct impact is called primary fiberization and is to be contrasted with secondary fiberization, which occurs when clumps of fibers torn from the fibrous sheets are rubbed by the rotor against screens or casing or casing protuberances which normally surround the rotor and are separated into individual fibers.
Heretofore, various patterns have been proposed for impact elements on the periphery of disintegrator rotors. In Sakulich et al, U.S. Pat. No. 3,519,211, teeth are arranged such that successive rows are offset and the time between successive impacts by the tips of the teeth is a minimum of about 0.4 milliseconds.
According to Buell, U.S. Pat. No. 3,824,652, it is preferred to have teeth randomly disposed on the rotor periphery and a reasonable approximation thereof is said to consist of multiple sets of teeth in helical patterns with helical angles of 10 degrees to 35 degrees and with teeth equidistant in all directions. One disclosed arrangement has a second adjacent set of teeth bearing a helical pattern which is an approximate mirror image of the pattern in the first portion, offset slightly, and in which the teeth are maintained about five widths apart in order to avoid poor fiberization due to one or more teeth being too
close together.
Banks, U.S. Pat. No. 3,637,146, discloses impact elements having a beveled face.